1. Field of the Invention
The present invention relates to a scheduler installed in a controller of a substrate processing apparatus having a plurality of processing sections and a plurality of substrate transfer devices which transfer substrates that are introduced into the substrate processing apparatus successively to the processing sections to process the substrates, a substrate processing apparatus, and a method of transferring substrates in a substrate processing apparatus.
2. Description of the Related Art
Various types of substrate processing apparatus are known in the art. According to one type of substrate processing apparatus which is widely used, a plurality of substrates are successively carried out of a substrate cassette into the substrate processing apparatus and then transferred between a plurality of processing units (processing sections) by a plurality of transfer devices to process the substrates parallel to each other, after which the fully processed substrates are retrieved by the substrate cassette. Another type of substrate processing apparatus includes a plurality of substrate cassettes which can be mounted in place and replaced with other substrate cassettes. When any substrate cassette has retrieved processed substrates, it is replaced with a substrate cassette containing unprocessed substrates, so that the substrate processing apparatus can be operated continuously for processing substrates uninterruptedly.
Some substrate processing apparatuses, typically substrate plating apparatuses for forming bumps or TSVs (Through Silicon Vias) or plating re-interconnect films, are required to achieve a high production quantity, i.e., a large number of substrates processed per unit time including a recovery time from a fault, while at the same time satisfying a strict process limiting condition, i.e., a predetermined process time interval after the end of a process until the start of a next process. To meet such strict requirements, there have been proposed various scheduling schemes, e.g., a linear programming scheduler and a simulation process scheduler, for making a substrate transferring plan that is optimum for substrate transferring control in substrate plating apparatus (see Japanese laid-open patent publication No. 2001-319842 and Japanese patent 3995478).
A linear programming scheduler based on a linear programming process is an excellent scheduling process for achieving a maximum throughput while satisfying a strict process limiting condition. The linear programming scheduler is required to produce a substrate transferring schedule according to a linear programming process by formulating, in advance, a process limiting condition and a nonnegative condition such as transferring pause so that the substrate processing apparatus will finish its process on a plurality of substrates supplied thereto at the fastest rate. Therefore, the linear programming scheduler needs to maximize a regular transferring capability for transferring the substrates without fail.
On the other hand, a simulation process scheduler based on a simulation process does not guarantee a maximum throughput unlike the linear programming scheduler. However, the simulation process scheduler is advantageous in that it can flexibly produce a substrate transferring schedule for, e.g., retrieving substrates while satisfying a process limiting condition at events including a production resumption, a dynamic switching between the use and nonuse of a unit, and a substrate process failure.